1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 * Copyright 2023 Bill Sommerfeld <sommerfeld@alum.mit.edu>
26 */
27
28 #pragma weak _closefrom = closefrom
29 #pragma weak _fdwalk = fdwalk
30
31 #include "lint.h"
32 #include <ctype.h>
33 #include <stdlib.h>
34 #include <unistd.h>
35 #include <string.h>
36 #include <fcntl.h>
37 #include <dirent.h>
38 #include <limits.h>
39 #include <errno.h>
40 #include <alloca.h>
41 #include <sys/resource.h>
42
43 /* Initial size of the open file descriptor array */
44 #define FDS_SZ (1024 * sizeof (int))
45
46 /*
47 * Iterate over all open file descriptors, calling 'func' on each one.
48 * Terminate the iteration when 'func' returns non-zero or when all
49 * open file descriptors have been processed. Return the value of
50 * the last non-zero return from 'func' or zero.
51 */
52 int
fdwalk(int (* func)(void *,int),void * cd)53 fdwalk(int (*func)(void *, int), void *cd)
54 {
55 int err = errno;
56 int rv = 0;
57 int max_fds = INT_MAX;
58 struct rlimit rl;
59 DIR *dirp;
60 struct dirent64 *dp;
61 int *fds;
62 size_t fds_sz;
63 int nfds;
64 int i;
65
66 nfds = 0;
67 fds = alloca(FDS_SZ);
68 fds_sz = FDS_SZ;
69 if ((dirp = opendir("/proc/self/fd")) != NULL) {
70 /*
71 * Collect all of the open file descriptors and close
72 * the directory before calling 'func' on any of them.
73 */
74 while ((dp = readdir64(dirp)) != NULL) {
75 /* skip '.', '..' and the opendir() fd */
76 if (!isdigit(dp->d_name[0]) ||
77 (i = atoi(dp->d_name)) == dirp->dd_fd)
78 continue;
79 if (fds_sz <= nfds * sizeof (int)) {
80 fds = memcpy(alloca(fds_sz * 2), fds, fds_sz);
81 fds_sz *= 2;
82 }
83 fds[nfds++] = i;
84 }
85 (void) closedir(dirp);
86 } else {
87 /*
88 * We could not open the /proc file descriptor directory.
89 * We have to do it the hard way.
90 */
91 if (getrlimit(RLIMIT_NOFILE, &rl) == 0)
92 max_fds = (rl.rlim_max == RLIM_INFINITY)?
93 INT_MAX : rl.rlim_max;
94 for (i = 0; i < max_fds; i++) {
95 if (fcntl(i, F_GETFD) < 0)
96 continue;
97 if (fds_sz <= nfds * sizeof (int)) {
98 fds = memcpy(alloca(fds_sz * 2), fds, fds_sz);
99 fds_sz *= 2;
100 }
101 fds[nfds++] = i;
102 }
103 }
104
105 /*
106 * Restore the original value of errno so that
107 * the caller sees only the value of errno set
108 * by the callback function.
109 */
110 errno = err;
111
112 /*
113 * Perform the callbacks on all of the open files.
114 */
115 for (i = 0; i < nfds; i++)
116 if ((rv = func(cd, fds[i])) != 0)
117 break;
118
119 return (rv);
120 }
121
122 /*
123 * Call-back function for closefrom(), below.
124 */
125 static int
void_close(void * lowp,int fd)126 void_close(void *lowp, int fd)
127 {
128 if (fd >= *(int *)lowp)
129 (void) close(fd);
130 return (0);
131 }
132
133 /*
134 * Close all open file descriptors greater than or equal to lowfd.
135 */
136 void
closefrom(int lowfd)137 closefrom(int lowfd)
138 {
139 int low = (lowfd < 0)? 0 : lowfd;
140
141 /*
142 * Close lowfd right away as a hedge against failing
143 * to open the /proc file descriptor directory due
144 * all file descriptors being currently used up.
145 */
146 (void) close(low);
147 (void) fdwalk(void_close, &low);
148 }
149